Epidemiologic work performed by others, as well as animal studies performed by our laboratory, indicates that enhanced folate status decreases the progression of colonic carcinogenesis in individuals who are pre-disposed to colon cancer. This is a prospective, placebo- controlled trial to examine whether folate supple mentation reduces certain intermediary markers of colonic neoplasia (ie: proliferative index of rectal mucosa, DNA methylaiton of rectal mucosa, c-myc oncogene expression) in such individuals.